JP7118754B2 - Straddle-type vehicle tail pipe structure - Google Patents

Description

The present invention relates to a tail pipe structure of an exhaust system for a straddle-type vehicle.

In a vehicle equipped with an engine, exhaust from the engine is muffled by an exhaust system and then discharged to the outside through a tail pipe at its downstream end. In straddle-type vehicles such as motorcycles, the exhaust system is exposed to the outside (for example, Patent Document 1).

JP 2008-025560 A

The larger the outer diameter of the outlet of the tail pipe of the exhaust system, the better the appearance. However, if the inner diameter of the outlet of the tail pipe is large, the exhaust noise becomes loud. In Patent Document 1, by covering the outlet portion of the tail pipe with a cover, the outlet portion with a large outer diameter is realized without increasing the outer diameter of the tail pipe. However, in the structure of Patent Document 1, a dead space occurs between the tail pipe and the cover.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a tail pipe structure for a saddle-ride type vehicle in which the peripheral portion of the exhaust outlet is enlarged to improve the appearance while effectively utilizing the space.

To achieve the above object, the tail pipe structure of an exhaust system for a straddle-type vehicle according to the present invention comprises an inner cylinder having an inlet port at its upstream end, an outer cylinder covering the inner cylinder, and a tail pipe inside the inner cylinder. a partition plate that is fixed to partition the interior of the inner cylinder into an inner cylinder upstream passage and an inner cylinder downstream passage; and an annular connecting member that connects the inner cylinder and the outer cylinder, the inner cylinder an outer passage is formed between the outer peripheral surface of and the inner peripheral surface of the outer cylinder, and the partition plate is formed with a first communication hole that communicates the inner cylinder upstream passage and the inner cylinder downstream passage, A second communication hole communicating between the inner cylinder upstream passage and the outer passage is formed in a portion of the outer peripheral wall of the inner cylinder on the upstream side of the partition plate. A first outlet through which the exhaust gas is discharged from the inner cylinder downstream passage is formed, and a second outlet through which the exhaust gas is discharged from the outer passage is formed at the downstream end of the outer passage. Here, "upstream" and "downstream" refer to upstream and downstream in the flow direction of the exhaust gas.

According to this configuration, since it has a double structure of the inner cylinder and the outer cylinder, the outlet portion of the tail pipe can be enlarged to improve the appearance. If the inner diameter of the outlet is increased, there is concern that the exhaust noise will increase, but in the above configuration, the exhaust is discharged from the first and second outlets. Therefore, the opening area of each outflow port does not become larger than the opening area determined by the inner diameter of the outlet of the tail pipe, so exhaust noise can be suppressed. In this way, it is possible to effectively utilize the space in the vicinity of the exit of the tail pipe to suppress an increase in exhaust noise, while enlarging the exhaust exit to improve the appearance.

In the present invention, a third communication hole may be formed in a portion of the outer peripheral wall of the inner cylinder downstream of the partition plate to communicate the inner cylinder downstream side passage and the outer passage. According to this configuration, the exhaust noise flowing into the inner cylinder downstream passage through the first communicating hole and the exhaust flowing into the inner cylinder downstream passage through the third communicating hole interfere with each other, thereby further suppressing exhaust noise.

When the third communication hole is provided, a plurality of the connection members are provided, at least one of the plurality of connection members is provided downstream of the third communication hole, and the connection member is provided with the A fourth communication hole may be formed to communicate between the upstream side and the downstream side of the connecting member in the outer passage. According to this configuration, it becomes easier for exhaust gas to flow into the inner cylinder downstream passage through the third communication hole, and exhaust gas interference can be effectively realized.

In the present invention, the first communication hole and the second communication hole may be composed of a plurality of through holes, and the total opening area of the second communication holes may be set to be equal to or larger than the passage area of the inner cylinder. According to this configuration, it becomes easier for the exhaust gas to flow into the outer passage from the second communication hole, and the flow of the exhaust gas is stabilized.

The present invention may further include a pipe cover that covers the outer cylinder, and the rear end of the pipe cover may extend rearwardly and inwardly in the vehicle width direction in a plan view. According to this configuration, the appearance in a side view from the outside in the vehicle width direction is good.

According to the tail pipe structure of the straddle-type vehicle of the present invention, it is possible to improve the appearance by enlarging the exhaust outlet while effectively utilizing the space.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a side view showing a motorcycle that is a type of saddle-ride type vehicle having a tail pipe structure according to a first embodiment of the present invention; It is a top view which shows the exhaust device of the same two-wheeled motor vehicle. It is the side view which looked at the same exhaust device from the other side of FIG. FIG. 3 is a cross-sectional view taken along line IV-IV of FIG. 2; FIG. 5 is a cross-sectional view taken along line VV of FIG. 4; FIG. 4 is a cross-sectional view taken along line VI-VI of FIG. 3;

Preferred embodiments of the present invention will be described below with reference to the drawings. In the following description, "upstream" and "downstream" mean "upstream" and "downstream" in the flow direction of exhaust gas. FIG. 1 is a side view showing a motorcycle, which is a type of straddle-type vehicle, having a tail pipe structure according to a first embodiment of the present invention. The body frame FR of this motorcycle has a main frame 1 forming a front half and a rear frame 2 forming a rear half of the body frame FR. The rear frame 2 is connected to the rear portion of the main frame 1 .

[Overall vehicle structure]
A front fork 4 is supported on the front end of the main frame 1, and a front wheel 6 is supported on the lower end of the front fork 4. - 特許庁A handle 8 is attached to the upper end of the front fork 4 . A swing arm bracket 10 is formed below the rear end of the main frame 1 . Front ends of a pair of left and right swing arms 12 are supported by the swing arm bracket 10 via pivot shafts 14 so as to be vertically swingable. A rear wheel 16 is supported at the rear end of the swing arm 12 . An engine E is supported in the lower center of the main frame 1 . Engine E drives rear wheels 16 via chains 18 .

A rider's seat 20 and a passenger's seat 22 are supported by the rear frame 2 . A fuel tank 24 is attached between the handle 8 and the rider's seat 20 on the upper part of the main frame 1 .

The engine E of this embodiment is a four-cylinder, four-cycle engine in which cylinders are arranged in the vehicle width direction. However, the type of engine E is not limited to this. The engine E has a crankcase 26 that supports a crankshaft (not shown), a cylinder 28 projecting upward from the crankcase 26, and a cylinder head 30 thereabove.

Four exhaust pipes 32 are connected to exhaust ports (not shown) on the front surface of the cylinder head 30 . Each exhaust pipe 32 extends downward on the front side of the engine E and then joins at a gathering portion 34 below the engine E. As shown in FIG. A muffler 35 is connected to the downstream end (rear end) of the collective portion 34 . The muffler 35 muffles the exhaust. A tail pipe 36 is connected to the rear end of the muffler 35 . Thus, the exhaust pipe 32, the collecting portion 34, the muffler 35, and the tail pipe 36 constitute the motorcycle exhaust system ED. The tail pipe 36 constitutes the outlet portion of the exhaust device ED.

[Muffler structure]
The muffler 35 of this embodiment is arranged between the rear surface of the engine E and the rear wheel 16 . A support bracket 38 is joined to the upper surface of the muffler 35 . The muffler 35 is supported by the lower end of the swing arm bracket 10 via a support bracket 38. As shown in FIG.

As shown in FIG. 2, an oxygen sensor 40 is provided at the front end (upstream end) of the collecting portion 34 . Oxygen sensor 40 detects the concentration of oxygen in the exhaust. A catalytic converter 42 is accommodated downstream (rear) of the oxygen sensor 40 in the collective portion 34 . The catalytic converter 42 renders harmful exhaust components such as hydrocarbons and carbon monoxide contained in the exhaust harmless. In this embodiment, two catalytic converters 42 are provided along the flow direction of the exhaust gas. However, the number of catalytic converters 42 may be one, or three or more. Also, the catalytic converter 42 may be housed within the muffler 35 .

The outer side (right side) of the muffler 35 is covered with a muffler cover 44 . Specifically, a mounting bracket 35a is joined to the right side surface of the muffler 35, and a muffler cover 44 is detachably attached to the mounting bracket 35a using a fastening member 45. As shown in FIG. The muffler cover 44 of the present embodiment covers the region from the middle portion in the longitudinal direction to the rear end portion of the muffler 35 and the front portion of the tail pipe 36 from the outside (right side).

FIG. 3 is a view of the muffler 35 viewed from the side (right side) opposite to that of FIG. As shown in FIG. 3, the muffler 35 of this embodiment has a so-called "monaka structure", which is formed by integrating an upper case half 37 and a lower case half 39 by welding.

4 is a sectional view taken along line IV-IV of FIG. 2, and FIG. 5 is a sectional view taken along line VV of FIG. As shown in FIG. 4, the muffler 35 is interposed between an inner case 46 in which an expansion chamber is formed, an outer case 48 covering the outer side of the inner case 46, and the inner case 46 and the outer case 48. It has a sound absorbing material 50 . The sound absorbing material 50 has heat resistance, impact resistance, and damping properties. In this embodiment, the inner case 46 and the outer case 48 are made of stainless steel, and the sound absorbing material 50 is glass wool. However, the material of the inner case 46, the outer case 48 and the sound absorbing material 50 is not limited to this.

In this embodiment, three expansion chambers 52 , 54 , 56 are formed inside the inner case 46 . More specifically, the interior of the inner case 46 is partitioned into three chambers in the front-rear direction by first and second partition walls 58 and 60, with the first expansion chamber 52 being formed at the rearmost and furthest upstream. A second expansion chamber 54 is formed in the front, and a third expansion chamber 56 is formed in the middle. However, the number and arrangement of expansion chambers are not limited to this.

As shown in FIG. 5, the first expansion chamber 52 is formed between the second partition wall 60 and the rear wall 46r of the inner case 46. As shown in FIG. The second expansion chamber 54 is formed between the front wall 46 f of the inner case 46 and the first partition wall 58 . A third expansion chamber 56 is formed between a first partition 58 and a second partition 60 . The first partition 58 and the second partition 60 are joined to the inner wall of the inner case 46 .

An introduction pipe 62 of the muffler 35 is connected to the downstream end of the collecting portion 34 . The introduction pipe 62 penetrates the front wall 48 f of the outer case 48 , the front wall 46 f of the inner case 46 , the first partition 58 and the second partition 60 and opens to the first expansion chamber 52 . In other words, the introduction pipe 62 passes through the second expansion chamber 54 and the third expansion chamber 56 to allow the inside of the collecting portion 34 and the first expansion chamber 52 to communicate with each other.

A first communication pipe 64 is provided that penetrates the second partition wall 60 and the first partition wall 58 and allows the first expansion chamber 52 and the second expansion chamber 54 to communicate with each other. One end (upstream end) of the first communication pipe 64 opens into the first expansion chamber 52 , passes through the third expansion chamber 56 , and the other end (downstream end) opens into the second expansion chamber 54 .

A second communication pipe 66 is provided that penetrates the first partition wall 58 and allows the second expansion chamber 54 and the third expansion chamber 56 to communicate with each other. One end (upstream end) of the second communicating pipe 66 opens to the second expansion chamber 54 , and the other end (downstream end) opens to the third expansion chamber 56 . Instead of the second communication pipe 66, an opening may be provided in the first partition wall 58 to allow the second expansion chamber 54 and the third expansion chamber 56 to communicate with each other.

A lead-out pipe 68 connected to the tail pipe 36 is provided through the second partition 60 , the rear wall 46 r of the inner case 46 and the rear wall 48 r of the outer case 48 . One end (upstream end) of the lead-out pipe 68 opens into the third expansion chamber 56 , passes through the first expansion chamber 52 , and the other end (downstream end) is connected to the tail pipe 36 . That is, the lead-out pipe 68 allows the third expansion chamber 56 and the inside of the tail pipe 36 to communicate with each other.

The introduction pipe 62 is joined to the front wall 48f of the outer case 48 and the front wall 46f of the inner case 46 by welding, for example. Similarly, the outlet pipe 68 is joined to the rear wall 46r of the inner case 46 and the rear wall 48r of the outer case 48 by welding, for example. The connection between other pipes and the fixing of the pipes to the bulkhead may be welding or press-fitting. The arrows in FIG. 5 indicate the flow of the exhaust gas G. As shown in FIG.

[Tail pipe structure]
FIG. 6 is a longitudinal sectional view of the tail pipe 36. As shown in FIG. As shown in FIG. 6, the tail pipe 36 has a double pipe structure having an inner cylinder 70 and an outer cylinder 72 . The inner cylinder 70 has an inlet 70a formed at its upstream end. Specifically, an inlet 70a at the upstream end of the inner cylinder 70 is connected to an outlet 68a at the downstream end of the outlet pipe 68 of the muffler 35 . In this embodiment, the downstream end of the lead-out pipe 68 is press-fitted inside the upstream end of the inner cylinder 70 .

The outer cylinder 72 covers the inner cylinder 70 . In other words, the inner cylinder 70 is inserted through the outer cylinder 72 . In this embodiment, the inner cylinder 70 and the outer cylinder 72 have a circular cross-sectional shape, but they may have an elliptical cross-sectional shape. In addition, the inner cylinder 70 and/or the outer cylinder 72 may have a tapered shape in which the passage area gradually decreases toward the downstream. The inner cylinder 70 and the outer cylinder 72 are connected by an annular connecting member 69 .

The connecting member 69 has a small-diameter tubular portion 69a, a large-diameter tubular portion 69b, and a ring portion 69c that connects the tubular portions 69a and 69b. A small-diameter cylindrical portion 69a of the connecting member 69 is welded to the outer peripheral surface of the inner cylinder 70 . The inner peripheral surface of the outer cylinder 72 is press-fitted into the outer peripheral surface of the large-diameter tubular portion 69 b of the connecting member 69 . In this embodiment, two connecting members 69 are provided side by side in the axial direction of the tail pipe 36 . The number of connecting members 69 is not limited to this. Further, in this embodiment, each connecting member 69 has the same shape. As a result, it is possible to suppress an increase in the types of components. However, the shape of the connecting member 69 may be different.

A partition plate 74 is fixed inside the inner cylinder 70 . The partition plate 74 partitions the interior of the inner cylinder 70 into an inner cylinder upstream passage 76 and an inner cylinder downstream passage 78 . The partition plate 74 has a cylindrical shape with a bottom, and its outer peripheral surface is press-fitted into the inner peripheral surface of the inner cylinder 70 . One or more first communication holes 75 are formed in the bottom plate 74 a of the partition plate 74 . The first communication hole 75 allows the inner cylinder upstream passage 76 and the inner cylinder downstream passage 78 to communicate with each other. In this embodiment, the first communication hole 75 is composed of a plurality of punched holes.

A second communication hole 80 is formed in a portion of the outer peripheral wall of the inner cylinder 70 upstream of the partition plate 74 . In this embodiment, the first communication hole 75 is composed of a plurality of punched holes. An outer passage 82 is formed between the outer peripheral surface of the inner cylinder 70 and the inner peripheral surface of the outer cylinder 72 . That is, the second communication hole 80 communicates the inner cylinder upstream passage 76 and the outer passage 82 . In this embodiment, the outer passageway 82 is an annular passageway. However, the outer passageway 82 need not be annular.

A first outlet 84 through which the exhaust gas is discharged from the inner cylinder downstream passage 78 is formed at the downstream end of the inner cylinder downstream passage 78 of the inner cylinder 70 . A second outflow port 86 through which the exhaust gas is discharged from the outer passage 82 is formed at the downstream end of the outer passage 82 . That is, the first outlet 84 and the second outlet 86 constitute the outlet of the tail pipe 36 .

The rear end of the tail pipe 36 extends inward in the vehicle width direction while being inclined rearward. That is, the rear ends of the inner cylinder 70 and the outer cylinder 72 extend inward in the vehicle width direction while being inclined rearward. 3, the first outflow port 84 at the downstream end of the inner cylinder 70 and the second outflow port 86 of the outer cylinder 72 look elliptical, and the appearance is good.

A third communication hole 85 is formed in a portion of the outer peripheral wall 70 b of the inner cylinder 70 on the downstream side of the partition plate 74 . The third communication hole 85 communicates the inner cylinder downstream side passage 78 and the outer passage 82 . In this embodiment, the third communication hole 55 is composed of a plurality of punched holes.

In this embodiment, one of the two connecting members 69 (upstream side) is provided upstream of the first communication hole 75, and the other (downstream side) is provided downstream of the third communication hole 85. . A fourth communication hole 90 is formed in the ring portion 69c of the connecting member 69 on the downstream side. The fourth communication hole 90 communicates between the upstream side and the downstream side of the downstream side connecting member 69 in the outer passage 82 . In this embodiment, the fourth communication hole 90 is composed of a plurality of through holes that are spaced apart in the circumferential direction.

In this embodiment, the ring portion 69c of the connecting member 69 on the upstream side is not provided with a through hole, but the ring portion 69c of the connecting member 69 on the upstream side may be provided with a through hole. Thereby, not only the shape but also the structure of the two connecting members 69 can be made the same. However, in the case of this embodiment, if a through hole is provided in the ring portion 69c of the connecting member 69 on the upstream side, the outer passage 82 and the storage space of the sound absorbing material 50 in the muffler 35 communicate with each other. must be provided. Moreover, if all the connecting members 69 are located at positions that do not affect the flow of the exhaust gas in the outer passage 82, it is not necessary to provide the through holes in the ring portions 69c of the connecting members 69. FIG.

The opening sizes of the first to fourth communication holes 75, 80, 85, 90 of this embodiment are as follows. S0 is the passage area of the inner cylinder 70, S1 is the total opening area of the first communication holes 75, S2 is the total opening area of the second communication holes 80, S3 is the total opening area of the third communication holes 85, and S3 is the total opening area of the third communication holes 85. Let S4 be the total opening area of the communication holes 90 . In the present embodiment, S2>S0>S1>S3>S4 are set. The passage area S0 of the inner cylinder 70 and the total area S2 of the openings of the second communication holes 80 may be the same. However, the relationship of the opening areas of the first to fourth communication holes 75, 80, 85, 90 is not limited to this embodiment.

The tail pipe 36 has a pipe cover 92 that covers the outer circumference of the outer cylinder 72 . The pipe cover 92 of this embodiment has a cylindrical shape and is fixed to the outer cylinder 72 at its front end (upstream end) 92a. Specifically, a cover attachment member 94 extending radially outward is provided on the outer peripheral surface of the front end portion of the outer cylinder 72 . A plurality (three in this embodiment) of the cover mounting members 94 are spaced apart in the circumferential direction, and are fixed to the outer peripheral surface of the outer cylinder 72 by welding. A threaded hole 94a is formed in each cover mounting member 94, and a front end portion 92a of the pipe cover 92 is detachably mounted to the outer cylinder 72 via the cover mounting member 94 using a fastening member 95 such as a bolt. there is In this embodiment, the threaded hole 94a is a weld nut.

An annular space SP is formed between the outer peripheral surface of the outer cylinder 72 and the inner peripheral surface of the pipe cover 92 . In other words, the outer cylinder 72 and the pipe cover 92 are not in contact with each other except indirectly through the cover mounting member 94 . Thereby, it is possible to suppress the heat of the outer cylinder 72 from being transferred to the pipe cover 92 . However, the pipe cover 92 may be omitted.

A rear end (downstream end) 92b of the pipe cover 92 extends obliquely rearward inward in the vehicle width direction in plan view according to the shapes of the inner cylinder 70 and the outer cylinder 72 . Further, in this embodiment, the rear end 92b of the pipe cover 92 is folded inwardly by 180°. Furthermore, in this embodiment, the radial width t1 of the annular space SP on the inner side in the vehicle width direction is set larger than the radial width t2 on the outer side in the vehicle width direction (t1>t2). The slanted structure, the folded structure, and the width dimension, together with the slanted shapes of the rear ends of the inner cylinder 70 and the outer cylinder 72, improve the appearance from the outside in the vehicle width direction shown in FIG.

[Assembling the tail pipe]
Next, assembly of the tail pipe 36 will be described. First, the partition plate 74 is press-fitted inside the inner cylinder 70 shown in FIG. A connecting member 69 is attached to the outer peripheral surface of the inner cylinder 70 . Next, the outer cylinder 72 is press-fitted onto the outer peripheral surface of the large-diameter cylinder portion 69 b of the connecting member 69 . Subsequently, the pipe cover 92 is attached to the outer peripheral surface of the outer cylinder 72 using the fastening member 95 . As described above, a sub-assembly of the tail pipe 36, which is composed of the inner cylinder 70, the outer cylinder 72 and the pipe cover 92, is constructed.

[Attaching the tail pipe to the muffler]
Next, a structure for mounting the tail pipe 36 (sub-assembly) to the muffler 35 will be described. As described above, the muffler 35 has a double structure consisting of the inner case 46 and the outer case 48 . An annular pipe mounting member 96 is provided on the inner peripheral surface of the downstream end portion 46 a that constitutes the outlet opening of the inner case 46 . In this embodiment, the pipe mounting member 96 is fixed to the inner peripheral surface of the downstream end portion 46a of the inner case 46 by welding. The downstream end of the outlet pipe 68 of the muffler 35 is press-fitted into the inner diameter surface of the pipe mounting member 96 .

In this embodiment, the outer diameter of the inner cylinder 70 and the outlet pipe 68 are set equal, and the inner diameter of the outer cylinder 72 and the inner diameter of the outlet opening (downstream end portion 46a) of the inner case 46 are set equal. Therefore, the same parts can be used for the connecting member 96 and the pipe mounting member 96 . This can prevent an increase in the types of parts.

The downstream end of the lead-out pipe 68 of the muffler 35 is press-fitted into the inner peripheral surface of the upstream end of the inner cylinder 70 of the tail pipe 36 (sub-assembly). As described above, the outer diameter of the inner cylinder 70 and the outer diameter of the lead-out tube 68 are set equal, but the upstream end of the inner cylinder 70 is slightly enlarged in diameter to facilitate press-fitting. In this state, the outer peripheral surface of the upstream end 72a of the outer cylinder 72 of the tail pipe 36 (sub-assembly) is welded to the inner surface of the downstream end 48a forming the outlet opening of the outer case 48 of the muffler 35. As shown in FIG. The upstream end (front end) of the outer cylinder 72 is enlarged in diameter so that it can be easily welded to the downstream end 48a of the outer case 48 . As described above, the tail pipe 36 (sub assembly) is fixed to the muffler 35 .

Furthermore, the muffler cover 44 is attached to the muffler 35 using the fastening member 45 shown in FIG. The muffler cover 44 covers the connecting portion between the muffler 35 and the tail pipe 36 and the fastening member 95 for attaching the pipe cover 92 from the outside (right side). This improves the appearance of the vehicle.

[Exhaust flow]
Next, the flow of exhaust gas in this embodiment will be described. When the engine E shown in FIG. 1 starts and the motorcycle runs, the exhaust gas G combusted in the cylinder 28 of the engine E is led out to the exhaust pipe 28 . The exhaust gas G is collected at the collecting portion 34 shown in FIG. 2 and then passed through the catalytic converter 42 to be purified.

Exhaust gas G that has passed through the catalytic converter 42 flows into the first expansion chamber 52 of the muffler 35 through the introduction pipe 62 shown in FIG. After being expanded in the first expansion chamber 52 , the exhaust gas G flows into the second expansion chamber 54 through the first communication pipe 64 . After being expanded in the second expansion chamber 54 , the exhaust gas G flows into the third expansion chamber 56 through the second communication pipe 66 . After being expanded in the third expansion chamber 56, the exhaust gas G is led out from the lead-out pipe 68 to the tail pipe 36 shown in FIG. In this manner, the exhaust gas G repeats expansion and contraction inside the muffler 35 and is muffled.

The exhaust G flows into the inner cylinder upstream passage 76 of the inner cylinder 70 from the inlet 70 a of the tail pipe 36 . Part of the exhaust gas G in the inner cylinder upstream passage 76 flows into the inner cylinder downstream passage 78 through the first communication hole 75 , and the rest flows into the outer passage 82 through the second communication hole 80 . In this embodiment, since the opening area S2 of the second communication hole 80 is larger than the opening area S1 of the first communication hole 75, most of the exhaust gas G flows from the second communication hole 80 into the outer passage 82, flows into the inner cylinder downstream passage 78 from the first communication hole 75 .

A portion of the exhaust G in the outer passage 82 flows into the inner cylinder downstream passage 78 through the third communication hole 85 , and the remaining portion passes through the fourth communication hole 90 and flows through the outer passage 82 . In this embodiment, since the opening area S3 of the third communication hole 85 is larger than the opening area S4 of the fourth communication hole 90, most of the exhaust gas G flows from the third communication hole 85 into the inner cylinder downstream passage 78. , part of which passes through the fourth communication hole 90 .

Exhaust interference occurs between the exhaust gas G flowing into the inner cylinder downstream passage 78 through the third communication hole 85 and the exhaust gas G flowing into the inner cylinder downstream passage 78 through the first communication hole 75, and exhaust energy is reduced. . As a result, the exhaust gas G is further muted. Exhaust gas G in the inner cylinder downstream passage 78 is discharged to the outside from the first outlet 84 . On the other hand, the exhaust gas G passing through the fourth communication hole 90 and flowing inside the outer passage 82 is discharged to the outside from the second outlet 86 .

[Action/effect]
According to the above configuration, the tail pipe 36 has a double structure of the inner cylinder 70 and the outer cylinder 72, so that the exit portion of the tail pipe 36 can be enlarged to improve the appearance. If the inner diameter of the outlet is increased, there is concern that the exhaust noise will increase. According to the above configuration, since the exhaust gas G is discharged from the first outlet 84 and the second outlet 86, compared to the cross-sectional area of the inner diameter of the outlet of the entire tail pipe 36 (the inner diameter of the outer cylinder 72), each outlet The opening areas of 84 and 86 can be small. Therefore, exhaust noise is suppressed. In this way, the space near the exit of the tail pipe 36 can be effectively used to suppress the exhaust noise from becoming louder, and the apparent exit of the exhaust gas G can be enlarged to improve the appearance.

In addition, since the exhaust gas G flowing into the inner cylinder downstream passage 78 through the third communication hole 85 and the exhaust gas G flowing into the inner cylinder downstream passage 78 through the first communication hole 75 interfere with each other, exhaust energy is reduced. decreases. As a result, the exhaust noise is further suppressed.

Furthermore, a connecting member 69 is provided downstream of the third communicating hole 85 in the outer passage 82 , and a fourth communicating hole 90 is formed in this connecting member 69 . As a result, the exhaust gas can easily flow into the inner cylinder downstream passage 78 from the third communication hole 85, and exhaust gas interference can be effectively realized. In addition, the connecting member 69 can prevent foreign matter from entering the outer passage 82 .

In addition, since the total opening area S2 of the second communication holes 80 is set to be equal to or larger than the passage area S0 of the inner cylinder 70, the exhaust gas G easily flows from the second communication holes 80 into the outer passage 82. stabilizes.

As shown in FIG. 3 , the rear end of the pipe cover 92 extends rearwardly inward in the vehicle width direction in plan view, so that the side view from the outside in the vehicle width direction has a good appearance.

The present invention is not limited to the above embodiments, and various additions, changes, or deletions are possible without departing from the scope of the present invention. For example, in the above embodiment, the tail pipe 36 of the muffler 35 having a monaka structure has been described, but the tail pipe structure of the present invention can also be applied to a muffler having a wound pipe structure. Further, in the above embodiment, an example in which the tail pipe structure of the present invention is applied to an exhaust system for a motorcycle has been described, but the tail pipe structure of the present invention can also be applied to an exhaust system for straddle-type vehicles other than motorcycles. . Accordingly, such are also included within the scope of this invention.

36 Tail pipe 69 Connecting member 70 Inner cylinder 70a Inlet 70b Outer peripheral wall 72 of inner cylinder Outer cylinder 74 Partition plate 75 First communication hole 76 Inner cylinder upstream passage 78 Inner cylinder downstream passage 80 Second communication hole 82 Outer passage 84 First outflow port 85 Third communication hole 86 Second outflow port 90 Fourth communication hole 92 Pipe cover 92b Rear end ED of pipe cover Exhaust device S0 Passage area S2 of inner cylinder Total opening area of second communication holes

Claims (3)

A tail pipe structure of an exhaust system for a straddle-type vehicle,
an inner cylinder having an inlet at its upstream end;
an outer cylinder covering the inner cylinder;
a partition plate fixed inside the inner cylinder and partitioning the inside of the inner cylinder into an inner cylinder upstream passage and an inner cylinder downstream passage;
An annular connecting member that connects the inner cylinder and the outer cylinder,
An outer passage is formed between the outer peripheral surface of the inner cylinder and the inner peripheral surface of the outer cylinder,
The partition plate is formed with a first communication hole that communicates the inner cylinder upstream passage and the inner cylinder downstream passage,
A second communication hole communicating between the inner cylinder upstream passage and the outer passage is formed in a portion of the outer peripheral wall of the inner cylinder upstream of the partition plate,
A first outlet through which exhaust gas is discharged from the inner cylinder downstream passage is formed in the inner cylinder downstream passage of the inner cylinder,
a second outlet through which the exhaust gas is discharged from the outer passage is formed at the downstream end of the outer passage;
A third communication hole is formed in a portion of the outer peripheral wall of the inner cylinder downstream of the partition plate, the third communicating hole communicating the inner cylinder downstream passage and the outer passage,
A plurality of the connecting members are provided,
At least one connecting member of the plurality of connecting members is provided downstream of the third communication hole, and communicates with the connecting member between the upstream side and the downstream side of the connecting member in the outer passage. A tail pipe structure for a straddle-type vehicle in which a communication hole is formed . 2. The tail pipe structure according to claim 1 , wherein the first communication hole and the second communication hole are composed of a plurality of through holes,
The tail pipe structure for a straddle-type vehicle, wherein the total opening area of the second communication holes is set to be equal to or larger than the passage area of the inner cylinder. 3. The tail pipe structure according to claim 1 , further comprising a pipe cover that covers the outer cylinder,
A tail pipe structure for a straddle-type vehicle, wherein the rear end of the pipe cover extends rearwardly inward in the vehicle width direction in plan view.

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